Abstract: Dynamic interactions among 20 billion cortical neurons generate, in ways that are still mysterious, phenomena we identify as language, memory and emotion. Alternative models have been proposed for linking the neural substrate of the brain to these mental phenomena. Each model has some merits, though none is perfect. Functional imaging has been particularly fruitful in addressing these issues. I will review some alternative approaches to the localization of function, based on patients with brain lesions, neuroanatomy, and functional imaging. I will focus on spatial attention as a model network and explore the value of the resulting principles for understanding the organization of other large-scale networks in the human brain.